And I'm affraid the only way you will get value out of a Wii game is if it is not a port of a current gen console, something made only for the Wii.
And, by the way, the Wii was never meant for games like COD. There is a FPS that is coming out for the Wii (The Conduit, I think it is called) that I'm sure will be better than a port of COD.
So in short, the Wii is only good for exclisives (which would be most of it's games). That said their are some good titles out there. Madworld being the obvious first. RE4 if you haven't already played it (I played it on GC and played it again on Wii, I liked the Wii version much better). Okami (a port from PS2, but a really good one).
I would advise you keep your Wii, and save up for a new console. Chicks dig a Wii (my wife loves it). Can't imagine you would get much for a used Wii anyway (definately not enough for a new console). But if you move to a new console, I would suggest the 360. I have both PS3 and 360, and my 360 gets much more use. Yes you have to pay for online service, but the 360 online is much better than PS3, plus, people use mics (not so on PS3). Also, I like the 360 exclusives better (save for Killzone 2).